Breast cancer ranks second as a cause of cancer death in women. The high mortality rate of breast cancer is attributed to difficulties associated with early detection, prognosis, and effective treatment. We propose to study a novel p53/hsa-miR-181d/DEPTOR axis as the critical regulator of the oncogenic balance in breast cancer. DEPTOR is an inhibitor of mammalian target of rapamycin (mTOR), which is an important oncogene that integrates growth-factor signals and metabolic stresses, and transduces them to downstream signaling pathways to promote cell growth, survival, and metastasis. DEPTOR is increasingly being associated with the progression of cancers. DEPTOR has been shown to promote cancer cell survival via PI3K/Akt activation in multiple myeloma (MM) patients, and subsequently linked to growth-promoting activities. Thus, despite its function and ability to suppress mTOR pathway, DEPTOR can function as a tumor promoter by activating the PI3K/Akt axis. Since p53 is a negative regulator of the PI3K/Akt pathway and functions as the master tumor suppressor that overpowers multiple oncogenic pathways, we hypothesize that p53 is involved in modulating DEPTOR functions. Further, based on strong preliminary data we hypothesize that deptor functions as an oncogene in human breast cancer and is regulated by novel p53-miR-181d axis. The anti-deptor miR- 181d is a p53-transcriptional target and functions as a tumor suppressor. The proposed project is highly innovative on all the fronts involving, study design (conceptual, research, and technical), advance (basic science, clinical science, and translational), and overall impact of the expected results for cancer treatment. Further the proposal is designed to cover both the K99 phase and R00 phase of research. Innovative clinical science discovery (K99 phase): We propose to establish deptor, miR-181d, and both in combination as novel and high-efficiency biomarkers for early cancer detection and patient prognosis. We will conduct thorough clinical studies to identify the predictive biomarker capacity of the miR-181d/DEPTOR axis. Innovative basic science discovery (K99+R00 phase): Study of the role of p53/miR-181d/DEPTOR axis as a critical oncogenic balance for tumorigenesis in humans is a novel, highly innovative, and groundbreaking research concept. This research will provide innovative insights into the mechanism regulating deptor and molecular mechanisms, through which deptor influences oncogenesis. Innovative translational science discovery (R00 phase): Both deptor and miR-181d are high-efficiency, high-priority, novel, innovative, and groundbreaking targets for breast cancer therapy with profound effects on regression of human tumor xenografts. Technical innovations: (i) Generation of deptor-null and miR-181d-null cell lines. This will generate genetically tractable tumor xenograft models for epigenetics study. (ii) Next-gen RNA-sequencing including long noncoding RNA seq in genetically modified deptor-/- and deptor-overexpressing tumor xenografts to study the oncogenic signaling of DEPTOR. In conclusion our proposed research design will use both the K99 and R00 phase to establish that DEPTOR and miR-181d can serve as high-efficiency prognostic biomarkers in breast cancer patients. The expected results will open new avenues for discovery of novel and groundbreaking early-detection biomarkers, biomarkers for all stages, patient prognosis biomarkers, and patient prediction biomarkers. The proposal contains research design and strategy to establish that the oncogenic versus tumor suppressor balance is critically regulated by the DEPTOR and miR-181d axis, and targeting DEPTOR and miR-181d has the potential to provide groundbreaking therapeutic strategies for breast cancer.